A possible problem with this idea is that the actual cost of provisions varies depending on how available it already is in the given locale (although, having said this, I think every item has a fixed “worth” that’s shown for reference). Still, I don’t think that every character should mindlessly become happier or sadder depending on the base “worth” of a provision. As we know, a more rare and expensive weapon isn’t always a genuine upgrade on cheaper and more common alternatives.
Also, the nutritive benefit of various foods can truly depend on how they’re prepared etc. Grains, for example, actually have various anti-nutritive properties (e.g. phytic acid) which can be diminished (thus increasing the nutritive benefit) by certain processing methods. But those anti-nutritive properties wouldn’t matter much if there were other items in the diet (e.g. cheese, venison) that over-compensated with an abundance of the affected nutrients (i.e. the nutritive value of one provision would really be relative to the availability of others).
But what if a character had coeliac disease or a dairy allergy? OMG …
Things like cheese and venison would have a high nutritive value generally, but they don’t have any carbs, and it would be difficult to keep running up hill hitting people on the head and forming shieldwalls without any carbs at all (so, again, the potential benefit of some provisions would be relative to the availability of others).
How high in alcohol are beer and mead? If they’re only super-low in alcohol, like most medieval ale, they might steadily enhance mood and resolve without having any anti-nutritive effect. Also, traditionally produced beer is likely to have a reasonable quantity of some B vitamins and thus might be of quite decent nutritive value.
